The invention relates to hinge joints in general, and more particularly to improvements in hinge joints which can be utilized with advantage between the adjustable back rests and the body supporting portions of seats, such as the driver's seat or the passenger seat next to the driver's seat in a motor vehicle.
A hinge joint which is used between the back rest and the body supporting portion of the seat in a motor vehicle normally comprises a first component or leaf which is affixed to the body supporting portion, a second component or leaf which is affixed to the back rest, a pintle which pivotally connects the second component with the first component, and a mechanism which can pivot the second component and the back rest relative to the first component and can maintain the back rest in a selected angular position. Reference may be had to commonly owned U.S. Pat. No. 4,371,207 granted Feb. 1, 1983 to Wilking et al. for "Position adjuster for motor vehicle seats and windows". The hinge joint of this patent employs a motion transmitting member which is rigid with the pintle and is partially surrounded by two substantially wedge-like arcuate sections which, in turn, are surrounded by a cylindrical internal surface of the first component. The sections are biased by a spring which urges their external surfaces against the internal surface of the first component. These sections can be said to constitute an eccentric which serves to maintain a spur gear of the first component in partial mesh with an internal gear of the second component. The central portion of the pivotable second component is rotatably mounted on a cylindrical portion of the pintle. The hinge joint of Wilking et al. is designed to establish one or more clearances which are intended to reduce friction during adjustment of the second component and back rest relative to the first component and body supporting portion of the seat. The clearance or clearances should develop when the adjustment begins, and such clearance or clearances should disappear when the adjustment of the back rest relative to the body supporting portion of the seat is completed. Nevertheless, each adjustment of the inclination of the back rest necessitates the exertion of a rather pronounced force because the engagement between the second component and the pintle suffices to generate a substantial amount of friction which must be overcome by the person seeking to change the inclination of the back rest.